Per request Nordic Hardware compiled this guide that shows you how to overclock Radeon HD 2900 XT when running two of them in CrossFire mode. Usually you would need BIOSes and a flash tool to do this, but we've got a way to work around this.
"We've received many e-mails ? the last few months regarding how to overclock two Radeon HD 2900 XT in CrossFire mode. Unfortunately we haven't had a good answer for you, but with some help from macci, now a resident of AMD/ATI, we can now present this guide, which shows you how to overclock Radeon HD 2900 XT when you have two of them running in CrossFire mode."
